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Windy Wellington & Rivers of Wind
18.06.04
I found this
interesting article from an old New Zealand windsurfing magazine about
1995 about wind in New Zealand. The article written by Bob McDavitt,
then forecast Manager for Metservice looks at the standard wind flow
patterns windsurfers should know about.
New
Zealand Wind Statistics 1971-2000
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Wind
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Gale days
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mean speed
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mean speed
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at least
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Location
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km/h
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63km/h
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KAITAIA
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15
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2
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WHANGAREI
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16
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1
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AUCKLAND
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17
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2
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TAURANGA
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16
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5
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HAMILTON
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12
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2
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ROTORUA
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13
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1
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GISBORNE
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15
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2
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TAUPO
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13
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2
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NEW PLYMOUTH
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20
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5
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NAPIER
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14
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3
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WANGANUI
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18
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5
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PALMERSTON NORTH
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17
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3
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MASTERTON,
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11
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1
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WELLINGTON
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22
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22
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NELSON
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12
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2
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BLENHEIM
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13
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4
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WESTPORT
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11
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2
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KAIKOURA
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15
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28
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HOKITIKA
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11
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2
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CHRISTCHURCH
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15
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3
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MT COOK
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10
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5
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LAKE TEKAPO
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7
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1
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TIMARU
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12
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6
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MILFORD SOUND
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9
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9
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QUEENSTOWN
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12
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2
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ALEXANDRA
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6
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3
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MANAPOURI
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10
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not measured
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DUNEDIN
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15
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8
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INVERCARGILL
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18
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18
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CHATHAM ISLANDS
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25
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16
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SCOTT BASE
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21
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27
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Windsurfing is a choice sport ... the fun you set
depends on your own choosing. When it comes to equipment, one hundred
dollars doesn't so far. But when it comes to weather spending just
one dollar can make your day. For starters, there are the marine forecasts
issued by Metservice. www.metservice.co.nz.
Forecasts come from Isobar-Land
Weather forecasting is a fascinating business... New Zealand has a
continuing chaotic clash between winds from the hot subtropics and
winds from the chilly subAntarctic. We use the KISS principle with
our forecasts: keep it short and simple. Look upon the forecast as
being an idea (coming from the brain of the best weather pattern picker
in the business), based on behaviour of a pattern on a weather map.
And a weather map (also called isobar-land) is only an approximation
of the real world.
It is up to you to combine the words of the weather forecast with
your own ideas and to fine-tune the forecast to your own location.
Local knowledge and observations of local weather signs (such as animal
behaviour) help. There's nothing like a bit of reality to help you
choose where the wind is best.
Winds in the real world
Windsurfers often observe local winds that differ from the smoothed-out
forecast. Wind in the real world accelerates down valleys, bumps about
abutments, bends around a bend, becomes contorted by a wiggly coastline,
dips and dives over hills and dales, eddies behind islands, and gallops
through saps. During a clear night, the land cools quickly so that
wind near the ground becomes sluggish. During a quiet sunny day, the
land heats quickly and air is drawn onshore (sea breezes). Terrain
effects can halve or double the forecast wind.
One trick that all windsurfers should always be on the look-out for
is a phenomenon which has been called "rivers of wind" :
These occur over the sea at the downwind end of a long range of mountains.
These rivers are strongest when there is a HIGH on the weather map
and isobars are drawn across the mountains. The wind can not follow
the isobars through the mountains, and a HIGH may restrict airflow
up and over the mountains, so that a lot of the air that collects
up-wind of the mountain chain can only exit around the ends or through
the gaps... and this wind blows best once it reaches the open sea.
Where and when is the best wind?
Wind is the main element of your fun. Most of New Zealand wind comes
from the Tasman Sea and is moulded by the mountains to give different
wind patterns to different locations. A graph of averaged out wind
speed from various airports and for each season of the year shows
some interesting points. Spring is the windiest time and autumn/winter
are (on average) the least windy. During summer easterly winds rule
north of Auckland and sea breezes dominate in Nelson, Hawke's Bay
and Canterbury. fan El Nino weather pattern impinges itself upon the
Pacific, then there are more (and stronger than average) southwest
winds for the whole country.
Wellington
Easily tops the list. It's located next door to Cook Strait and is
a perfect example of wind galloping through the gaps. Direction is
generally either from the northwest or from the south. The trick here
is to look at the difference in pressure (read the isobars) between
Wellington and Kaikoura. The wind in Wellington blows from high pressure
to low pressure and its speed is directly related to this pressure
difference.. In a southerly, multiply this difference by 10 to set
the Cook Strait wind speed in knots (so, if isobars between Wellington
and Kaikoura are 5 hectoPascals apart go for 50 knots through Cook
Strait).
Taranaki
This place is treasured with wind. It has wind even when the weather
situation is not proclucing much wind elsewhere. In a westerly flow
the breeze sets a boost from air which has collected upwind of the
Southern Alps and is diverted off to the north. In a southerly or
easterly flow, the river of wind coming from Cook Strait in joined
by wind pushing through Manawatu Gorge and, because of the mountain,
most of this air has to sqeeze around the south coast of Taranaki.
Auckland
Suprisingly more windy than lnvercargill (on average). But lnvercargill
is more gusty. In the greater Auckland recreational area (which includes
the Hauraki Gulf) winds gust to 60 km/hr or more about 180 days each
year. The best weather pattern worth checking for a good windsurfing
breeze in Auckland is the approach of a low or front from across the
central Tasman sea. This situation brews a useful northerly breeze
which is channelled to some extent by the islands of the Hauraki Gulf
and works best on the East Coast Bays. The trick is to check your
barometer... falling pressure indicates that the isobars are on the
move and the front or low is on track.
The other main breeze around Auckland is a southwesterly, which is
gusty and showery when strong. As an example of terrain effects on
the wind flow, we have compiled a map showing the pattern over the
Auckland area that should correspond to a forecast wind of "southwest
15 knots". Note that the Manukau Heads make a nozzle which squirts
wind all the way across Mangere Bridge, Howick and then into Tamaki
Strait. So tryout Onehunga or Tamaki Strait for the strongest winds
during a southwesterly. Note also that the wind splits in direction
between Waiheke and the Coromandel Peninsula, making a wind hole.
Christchurch
Three main wind directions : northeasterlies, northwesterlies and
southwesterlies. The locals call the northeast wind a "beasterly
easterly" because it is cool and cloudy. However, it is a steady
breeze, great for windsurfing, usually about 20 knots in Lyttleton
Harbour and 15 knots over the Estuary.
"Northwesterlies" have come from over the mountains and
are warm,dry and unsteady. "Southwesterlies" are cold, gusty
and sometimes showery.
Dunedin
On summer days the northeasterly sea breeze is common and it funnels
down the harbour steadily at 20 knots. Westerly winds occur often
but are gusty.
Invercargill
Perhaps too much swell on the southem beaches, so try the estuary
but watch the tide. Westerlies are the rule here during spring and
summer.
No matter where you are in New Zealand, there is a wind pattem that
makes your place the best. Some places are gifted with these pattems
more often than others.
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